Attachments are files that are attached to electronic mail (email) messages. Typically, such email messages include text and an icon that represents the attachment. A user may gain access to the contents of the attachment by performing a designated operation (such as double clicking) on the icon that represents the attachment. In response to the designated operation, an application program associated with the type of attachment is activated to display the contents of the attachment. For example, if the attachment is a word processing document, double clicking on the icon for the attachment causes a word processing application program to begin executing and the contents of the word processing document are displayed within a window of the word processing application program.
Attachments can be quite large. As a result, emails with attachments may occupy a great deal of memory space. Moreover, transmitting emails with large attachments over communication pathways that have limited throughput can be particularly slow. For example, dial-up connections often have limited baud rates, and it may take an excessive amount of time to download an email message that contains a large attachment over such dial-up connections. Unfortunately, a party has no way of knowing beforehand whether an email contains an attachment or not. Hence, a party may have to unwittingly wait a long period of time when attempting to download email messages over a dial-up connection.
Another difficulty with large email attachments is that the attachments may require a substantial amount of memory space to store them. For example, suppose that a single email message containing a large attachment is sent to ten recipients. In such an instance, ten copies of the attachment must be stored at one or more locations within the system. If all of the emails are stored on a single server, ten copies of the attachment must be stored on the server. Ultimately, in instances where email messages are stored on recipient computer systems, a large amount of memory on each of the recipient computer systems is occupied by the attachment.